Atheism claims that God does not exist. It does not claim anything about the usefulness of religion, or even the usefulness of believing that God exists. You can be an atheist and believe that religion should be treasured for its social benefits. You can feel the same way about mere belief in God’s existence. There are such atheists. You can believe in God and hate religion with a passion. Some believers do. And of course the smartest believers are smarter than the dumbest atheists. Irrelevancies aside, is there a case for atheism?

Atheism emerges from a two-stage argument. The first establishes that belief in God is unjustified. The second establishes that denial of God is justified: though the first stage doesn’t prove there is no God, it proves enough to justify the assertion that He does not exist.

Belief in God is unjustified because there is no reason to believe in God. There are alleged proofs of God’s existence: the ontological and cosmological proofs. The ontological proof is too abstruse to merit discussion here; it has little currency among believers. The cosmological proof says that there must be a first cause, namely God. But there is no reason why a first cause should be Godlike, nor why it has to be assumed.

To be a cause is to explain an event, and to explain an event is to give an account of how it came about. But positing any sort of first cause explains nothing; it simply places an entity for which there is no explanation at the start of a causal chain. So the cosmological proof has no force.

The other reasons alleged for belief in God are faith, and the order of the Universe. Faith is not only not reason; it is also not a reason to believe in something. Faith that there is a God may feel different from faith that your team will win, but no feeling, whatever its intensity or quality, can make non-evidence into evidence. We know the most intense faith can be wrong about worldly matters – why should it be more reliable on much tougher issues?

The only remotely plausible ground for believing in God is also the most popular: that there is some sort of design in the Universe. This doesn’t prove that a God designed nature, but it doesn’t have to, because if nature has a designer, God is a pretty good guess.

Atheists respond by arguing that the biological order in nature is better explained by selective adaptation than by design. This seems right, but it doesn’t justify atheism. For one thing, for the last 300 years there have been theists – “deists” – who hold that God operates through the laws of nature; perhaps He designed through natural selection. For another, even a good case for the best explanation doesn’t eliminate all the runners-up. That we should prefer the best explanation is a methodological rule of thumb, not a mathematical certainty or an unshakable dictate of experience. Worse, philosophers of science have a hard time explaining exactly what makes an explanation “best”: the criterion inevitably involves slippery concepts like “elegance”, “systematic power” and “informativeness” which so far have eluded precise definition. Perhaps this is why Dawkins, for instance, espouses something less than atheism. Like the bus signs, he says “there is probably no God”, which doubts rather than denies God’s existence.

If we’re more cautious about our arguments, we can be less cautious in our conclusions. Before we argue about design in nature, we need to know what counts as evidence for design. Nature, we will find, offers us no such evidence. This not only refutes the argument from design; it gives us enough reason to profess atheism.

When we ask for evidence, it has to be the sort that is available to us, not, say, time-travellers, or aliens who can detect radiation we can’t. For all we know, there are beings who’ve encountered evidence for design in nature. But what counts is whether there is evidence for us, and there isn’t.
What can we take as evidence of design? We have to start with things we are quite certain are indeed designed. Other things offer evidence of design to the extent they resemble the certain ones. None of the evidence is utterly conclusive: even if we see someone making a dress out of a pattern, yes, we might be hallucinating. But whatever its certainty, the evidence will fall into one of two categories. There is the evidence of provenance, and the evidence of pattern.

If we can trace the provenance of an object to a known production process, then we know it’s designed. It doesn’t matter what the object looks like. If we find an irregular-shaped piece of clay, and hear from trustworthy friends that this was in fact the work of an artist, and ask the artist about it, who says he made it but threw it out, we have strong evidence that the piece of clay was designed.

In nature, we have no evidence of provenance. We don’t see God building sea urchins; we don’t even have reports of Him doing this. The urchin doesn’t have a “made with pride by God” label on it. Those who claim to see God’s hand in things are making a metaphorical, not a literal assertion. So if we want evidence of design in nature, it has to be the evidence of pattern. But here is the make-or-break problem: nature provides no evidence of this sort.

The evidence of pattern consists entirely of resemblances to things known, through the evidence of provenance, to be designed. Mere order or function aren’t enough. If we had a very different spoken and written language, if nothing we made was shaped like the letters of our alphabet, we would have no reason to see design in a pattern like “EXIT”. Bicycles, clocks and scissors, unlike eyeballs, provide patterned evidence of design because we know, through the evidence of provenance, that people do design and manufacture such things. The more general the pattern, the weaker the evidence: cubes, for instance, are also found in some minerals, as are many other regular shapes. But a mineral-sized cube with some provenance, some pointers towards human practices, does provide evidence: not the bare cube, but the lettering on children’s blocks or the symbols and numbers on poker-dice.

Nature’s patterns exhibit order and complexity, but have no marks of provenance, nor any but the most general resemblance to things we know to be designed. If we found mammals shaped like BMWs or flowers shaped like scissors, that would be evidence of design. We don’t find anything like these items, so we have no such evidence. Even if thousands of factories started spewing out ordinary rocks, that wouldn’t help. Then we just wouldn’t know whether or not an ordinary rock was designed. Not knowing that something is designed isn’t good reason to suppose it’s designed. Since nothing in nature provides us with evidence of design, the argument from design cannot even get started.

This lack of evidence does not prove the non-existence of God. Despite this, it does much more than refute one argument: it gives us reason to espouse atheism. It makes sense to say, not “I don’t know if God exists” or even “There is probably no God”, but rather: there is no God. This has to do with when the conditions under which we feel entitled to assert something.
Whenever we say anything at all, we take it as understood that extreme scepticism can undermine our assertion. We’re entitled to deny that undetectable leprechauns ride on every raindrop, or that the statues on Mount Rushmore frequently recite French poetry, or that Mickey Mouse has a hidden kingdom in the Amazon. We can deny these things even though we know that, strictly speaking, we could be wrong. We could all be hallucinating or have overlooked some crucial evidence. But these “metaphysical” uncertainties are already understood when we assert that something does not happen or exist.

It is misleading to bring this background metaphysical uncertainty into the foreground by speaking of probabilities. When we actually assert probabilities – “it will probably rain this week” – we base our claim on real-world observations. We might, for example, cite the observed frequency with which weather conditions like these produce rain. Probability assertions, in other words, are themselves based on evidence. They are not neurotically cautious moves to guard against outcomes which no observation gives us any reason to expect. We don’t say: “we probably don’t have tentacles”. We just say that we don’t. We don’t feel some need to cover our ass in case we’ve been hallucinating all these decades. So it should be with God’s existence. If we omit the “probably” from “we probably don’t have tentacles”, we should omit it from “there probably is no God”.

Is this too science-y? Too rationalistic? Stanley Fish cautions us against overconfidence in “scientifically grounded assertions of atheism”: “confronted with a choice between a flawed but aspiring religious faith or a spectacularly hubristic faith in the power of unaided reason and a progress that has no content but, like the capitalism it reflects and extends, just makes its valueless way into every nook and cranny.”

Fish is slashing at a straw man: scientific thinking rests on far more than “the power of unaided reason”. Observation isn’t reason, but it’s a huge part of science. So is imagination, which extends deeply not only into theory and experiment construction but also into mathematics, which cannot credibly be thought to involve logic or “linear” thinking alone. Moreover the choice of one theory over another is widely understood to involve such quasi-aesthetic considerations as power and elegance, which are invoked to decide between equally well-confirmed hypotheses. These considerations, and other epistemological norms, easily fit under the rubric of “values”. And if emotion has no place in scientific argument, it quite obviously has a lot to do with what motivates scientists to undertake one project rather than another. Last but not least, science has no proof of its most basic assumptions. Scientists often need to have faith in science, in their insights, abilities, goals and methods. In other words, science involves a full range of human mental activity. The difference is that science deploys imagination, emotion and faith in the service of discovery, not wishful thinking. What has been discovered entitles us to deny many things, including the existence of God.